The renin-angiotensin system (RAS) is a major regulator of blood pressure and electrolyte balance in animals and humans. Renin is the rate limiting enzyme of the RAS cascade and its synthesis is highly regulated at both the transcriptional, post-transcriptional and secretory level. Despite years of investigation, our understanding of the mechanisms regulating renin gene expression remained very incomplete. The purpose of this proposal therefore is to test the overall hypothesis that the enhancers found upstream of the renin gene along with their cognate transcription factors (and specific ligands), co-activators, and co-repressors play a major role in controlling the cell- and tissue-specificity of expression and the transcriptional responses to physiological cues. To test and expand upon this hypothesis we have developed the following three main specific aims: 1) test the hypothesis that individual transcription factors identified to bind to the renin enhancer are important modulators of renin promoter/enhancer activity and endogenous renin expression at baseline, and under conditions where renin expression is either stimulated or repressed, 2) test the hypothesis that two enhancers of transcription, the kidney enhancer (KE) and chorionic enhancer (CE) in the human renin 5'flanking region are essential elements controlling tissue- and cell- specific expression and the responses to physiological cues, and 3) test the hypothesis that the transcription factors Ear2 (a negative regulator) and RARa (a positive regulator) are major determinants of renin expression in whole animals. With the development of new innovative technologies for interrogation of individual genes and proteins in both cells and whole animals, we are now poised for the first time to make important discoveries linking transcriptional events to specific physiological responses andpathways.